Preloaded pivot type feed for grinders



July 15, 1969 B. STROM ETAL 3,455,064

PRELOADED PIVOT TYPE FEED FOR GRINDERS Filed April 15, 1966 3 Sheets-Sheet 1 FIG. I.

FIG. 2.

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'INVENTORSI BERTI'L STROM OTTO WEISSING & Wanna July 15, 1969 a. STROM ETAL PRELOADED PIVOT TYPE FEED FOR GRINDERS Filed April 15. 1966 3 Sheets-Sheet 5 FIG.7.

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United States Patent 3,455,064 PRELOADED PIVOT TYPE FEED FOR GRINDERS Berti! Strom, Lutherville, and Otto Weissing, Towson, Md., assignors to SKF Industries, Inc., King of Prussia, Pa., a corporation of Delaware Filed Apr. 15, 1966, Ser. No. 542,848 Int. Cl. B24b /18, 5/00, 29/00 U.S. Cl. 51-103 6 Claims ABSTRACT OF THE DISCLOSURE In a grinding apparatus there is a base, work support means for rotatably supporting an annular workpiece, a grinding wheel assembly including an elongated pivot arm rotatably supporting a grinding wheel at one end and pivotally mounted to the base at its opposite end. In the grinding apparatus there is a stop member carried by the grinding wheel assembly on a line through the grinding wheel center or as closely adjacent to the center of the grinding wheel as practically possible, an infeed mechanism mounted on the base adapted to be engaged by the stop member of the grinding wheel assembly during the grinding cycle, actuator means for pivoting the grinding wheel assembly about its pivotal axis in a feed direction to maintain firm contact of the stop member and infeed mechanism during the grinding cycle, the infeed mechanism including means controlling pivotal movement of the grinding wheel assembly toward the workpiece during the grinding cycle, the point of contact between the stop member and infeed mechanism being located close to the grinding wheel center to minimize defiection.

This invention relates generally to grinding apparatus and more particularly to a new and improved preloaded pivot type feed arrangement for the grinding wheel assembly.

The present invention relates particularly to grinding apparatus used for grinding annular workpieces such as rings or rollers for rolling bearing assemblies. These grinders generally comprise a base, work support means for rotatably mounting or supporting the annular Workpiece and support and feed means for the grinding wheel assembly for selectively effecting movement of the grinding Wheel relative to the workpiece to effect grinding thereof. The grinding wheel assembly or wheel head is usually mounted on guideways such as sliding ways disposed generally transversely to the axis of rotation of the workpiece so that the wheel head moves in a straight line path transverse to the axis of the workpiece during the feed and retract cycle. These ways are usually protected by means of covers and wipers to keep out abrasive particles. Notwithstanding the provision of covers and wipers, it has been found that the ways tend to wear. Furthermore, another problem encountered with this type of feed arrangement for the grinding wheel assembly is the problem of stick-slip. This stick-slip characteristic may be described as a tendency of the wheelhead to alternately stick and slip during movement in the ways or as a chattering of the grinding wheel feed assembly in the way as it is being advanced toward the workpiece for grinding during the feed cycle.

This stick-slip characteristic is especially pronounced at very low feed velocities. Various attempts to overcome the problem of stick-slip have been utilized, including, for example lubrication of the ways with a lubricating oil having special additives. These attempts have been only partially successful and have not completely eliminated the problem of stick-slip motion in the feed mechice anism for the grinding wheel. It is noted that the accuracy and the finish of the workpiece is adversely affected by this stick-slip characteristic, friction and Wear of the Way-type grinding wheel feed mechanisms. Rolling and hydrostatic ways have been proposed in lieu of sliding ways and even though these are somewhat of an improvement over the sliding ways in terms of stick-slip and friction, they are comparatively expensive and have not completely overcome the problem.

In view of the above, it is a purpose of the present invention to provide an anti-friction feed arrangement for the grinding wheel assembly of a grinder which permits very low feed rates without slip-stick. To this end in accordance with the present invention, the grinding wheel assembly includes a pivot arm which rotatably supports the grinding wheel at one end and at its opposite end is pivotally supported in the base of the grinder. The grinding wheel assembly is angularly inclined toward the workpiece during the feed cycle whereby the weight of the assembly acts as a preloading force.

Further in accordance with the present invention, feed means is provided for positively urging the grinding wheel assembly about its pivotal axis to engage the workpiece during the feed or grinding cycle which, in the embodiment of the invention illustrated comprises an infeed mechanism and a piston cylinder actuator for positively maintaining the grinding wheel assembly in engagement with the feed screw of the infeed mechanism at a point remote from its pivotal axis. By this arrangement, the direction of infeed of the grinding wheel is above the horizontal plane of the work center so that the grinding force is transferred to the base of the grinder and the grinding wheel assembly is supported both above and below the line of contact of grinding to provide optimum stability and rigidity during the feed cycle. It has been found that this preloaded pivot arm arrangement overcomes the problems of wear and slip-stick, is relatively simple in structure, economical to make and maintenance free in operation.

Thus, an object of the present invention is to provide a grinder characterized by novel features of construction including a novel preloaded pivot type feed for the grinding wheel which eliminates the problems of stick-slip heretofore present in grinders and eliminates the problem of wear heretofore characteristic of the sliding ways.

Another object of the present invention is to provide a pivot type feed for the grinding wheel which utilizes gravity as a preloading force.

A further object of the present invention is to provide a grinder including a novel preloaded pivot type feed for the grinding wheel wherein the grinding wheel spindle is supported on opposite sides of a line of contact of grinding action for stability.

Still a further object of the present invention is to provide a grinder wherein the direction of infeed is disposed angularly above a horizontal plane of the work center so that the grinding force is directed toward the base of the machine.

A still further object of the present invention is to provide a grinder which is relatively simplified in construction, is economical to manufacture and is substantially maintenance free.

These and other objects of the present invention and the various features and details of the operation and construction thereof are hereinafter more fully set forth with reference to the accompanying drawing, wherein:

FIG. 1 is an end View of a grinder incorporating a grinding wheel feed arrangement in accordance with the present invention;

FIG. 2 is an enlarged sectional view of the pivotal mounting for the pivot arm of the grinding wheel assembly;

FIG. 3 is an enlarged sectional view taken on line 3-3 of FIG. 2;

FIG. 4 is a view looking in on line 4-4 of FIG. 3 showing the work support portion of the grinder;

FIG. 5 is a fragmentary side elevational view showing a sizing device for regulating the grinding cycle;

FIG. 6 is a sectional view of the sizing device taken on line 6-6 of FIG. 5; and

FIG. 7 is a schematic diagram of the sizing device control circuit.

Referring now to the drawings and with particular reference to FIG. 1 thereof, there is illustrated a grind ing apparatus generally designated by the numeral 10 incorporating a novel grinding wheel feed arrangement in accordance with the present invention. The grinding apparatus illustrated is for use in grinding workpieces W having a surface of revolution, for example a bearing ring or sleeve, and comprises a bed or base 12 and work support means for rotatably supporting the workpiece W therebetween. The work support means in the present instance includes a pair of work support heads 14 and 16 between which the workpiece W is supported, the work head 14 adapted to be rotated by suitable drive means and the work head 16 actuatable in an axial direction to facilitate positioning and removal of the workpiece W between the work heads. The Work head 14 includes a mandrel engaging interiorly of the workpiece in the manner shown in FIG. 4.

The grinding wheel assembly generally designated by the numeral 20 includes a spindle 22 mounted in an elongated tubular spindle housing 24, the spindle 22 mounting at one end the grinding wheel 26 and at its opposite end mounting pulleys 28 connected to the pulleys 34 on the output shaft of a motor 36 through a plurality of belts for rotation of the grinding wheel. The grinding wheel assembly further includes a shield or cover 38 of substantially half-moon shape having a cutout 40 to expose a portion of the grinding wheel 26 for the purpose of dressing the wheel.

*In accordance wtih the present invention, there is provided an antifriction feed arrangement for the grinding wheel assembly which permits very slow feed rates without stick-slip. To this end, the grinding wheel assembly 20 includes a pivot arm 42 pivotally mounted to the base 12 of the grinder along on axis XX which in the present instance is parallel to the axis of rotation YY of the grinding wheel and the axis of rotation ZZ of the workpiece. The feed arrangement further includes means for pivoting the grinding wheel about the pivot axis XX in one angular feed direction during grinding of the workpiece in an opposite direction to retract the grinding wheel assembly. In the present instance, the actuator means is a hydraulic piston cylinder actuator 43 wherein the cylinder is pivotally connected to the base as at 44 and the piston rod 46 is connected at its free end to the pivot arm 42 of the grinding wheel assembly.

Advance of the grinding wheel 26 relative to the workpiece during the feed cycle is controlled by an infeed mechanism 50 mounted on the base 12. The infeed mechanism 50, as best illustrated in FIGS. 1 and 3, includes a generally elongated, hollow housing 52, a feed screw 54 mounted in the housing which threadedly engages in an internally threaded retract cylinder 56 mounted in the forward end of the housing 52 and which is adapted to be engaged by a stop 58 carried by the grinding wheel assembly. The feed screw 54 mounts a worm gear 60 which is adapted to be rotated to actuate the retract cylinder '56 to permit advance of the grinding wheel by means including in the present instance a motor 62 connected through a transmission to a worm 64 which meshes with the worm gear 60.

The particular arrangement of the grinding wheel assembly, actuator and infeed mechanism provides the optimum conditions for grinding. For example, as best illustrated in FIG. 1, the pivotal axis XX of the grinding wheel assembly 20 is disposed in a first horizontal plane P below a second horizontal plane P through the axis of rotation ZZ of the workpiece and the axis of rotation YY of the grinding wheel 26 is above the horizontal plane through the workpiece during the feed cycle. By this arrangement, the direction of infeed of the grinding wheel 26 is above the horizontal plane P of the work center so that the grinding force is transferred to the base of the grinder.

Further, since the grinding wheel assembly is supported both above and below the line of contact of grinding, optimum stability and rigidity is provided during the feed cycle. Additionally, since the grinding wheel assembly 20 is inclined in a direction toward the Workpiece during the feed cycle by reason of the fact that the rotational axis YY of the grinding wheel is disposed between a vertical plane V through the axis of rotation XX of the grinding wheel assembly and the vertical plane V through the axis of rotation Z-Z of the workpiece. By this arrangement, gravitational weight of the grinding wheel assembly is used as a preloading force.

There is shown in FIGS. 5 and 6 a sizing mechanism generally designated by the numeral 70 for regulating the grinding cycle to grind workpieces to a predetermined finished size. This sizing mechanism includes a pivotally mounted link 72 which mounts a sensing nozzle 74 in close proximity to the peripheral surface of the grinding wheel. The position of the nozzle 74 relative to the grinding wheel during the grinding cycle is selectively adjustable by means of an adjusting screw S76. The control circuit for the sensing device is schematically illustrated in FIG. 7 and comprises a sensing and control device 76 to which the nozzle 74 is connected through a line 78 and a motor control circuit 80 for controlling operation of the feed mechanism 62, the motor control circuit 80 including a starting switch 81. The sensing and control device includes a pair of back pressure sensing switches or the like connected through pairs of leads 82 and 84 to the motor control circuit 80. The sensing and control device 76 also includes time delay circuit connected through leads 85 to the solenoid 86 of a control valve 88 for the pistoncylinder actuator 43 for the grinding wheel assembly 20. The control valve 88 is connected through a suitable line to a hydraulic pressure source 92.

Consider now the operation of the grinder and assume that the grinding wheel assembly 20 is in a fully retracted position wherein the rod 46 is fully extended. A workpiece W is then positioned between the workheads 14 and 16 and when so positioned (see FIG. 4) the work head 14 is actuated to rotate the workpiece W. The retract cylinder 56 of the infeed mechanism is then adjusted, for example by means of the hand wheel 61 for a given size workpiece so that rapid advance of the grinding wheel assembly is terminated just before the grinding wheel touches the workpiece Now with the workpiece supported, the feed cycle of the grinding wheel assembly 20 is initiated. This is accomplished simply by reversing flow of fluid in the actuator 43 through the valve 88 to retract the rod 46 and pivot the grinding Wheel assembly about the axis XX in a counterclockwise direction with respect to FIG. 3. The grinding wheel assembly 20 pivots rapidly in this direction until the stop 58 engages the retract cylinder 56 of the infeed mechanism 53. Now, when the starting switch 81 for the motor 62 is actuated, advance of the grinding wheel assembly 20 is controlled through the infeed mechanism, the screw 54 rotating at a predetermined rate to provide a preselected feed during the initial rough grinding cycle of the grinding operation. It is noted that the pivot arm 42 and the grinding wheel 26 advance during the feed cycle due to the force applied between the base 12 and the pivot arm 42 by the hydraulic actua tor 43 and the force of gravity. It is further noted that the direction of infeed of the grinding wheel relative to the workpiece is at an angle relative to a horizontal plane through the axis of rotation of the workpiece so that the grinding force is transferred to the base for optimum rigidity.

During the rough grinding cycle the gap between the grinding wheel 26 and nozzle 74 closes and at a predetermined back pressure, the first normally opened back pressure sensing switch closes at a predetermined back pressure to supply a signal to the motor control circuit 80 to shift the motor to a low speed, thus terminating the rough grinding cycle and initiating the finish grinding cycle. Finish grinding is terminated when the second normally opened back pressure switch of the sensing and control device 76 closes thereby generating a larger control signal to the motor control circuit to shut the motor off and prevent further infeed of the screw 54. Closing of the second back pressure switch also starts the time delay mechanism in the sensing and control device 76 -during spark out which after a predetermined time delay supplied a signal to the solenoid 86 to actuate control valve 88 to reverse flow in the piston-cylinder actuator 43 and effect pivotal movement of the grinding assembly away from the workpiece. The workpiece is then removed by retracting the work head 16. A new workpiece is then inserted and the infeed mechanism adjusted for grinding a new workpiece.

While a particular embodiment of the present invention has been illustrated and described herein, it is not intended to limit the invention to such disclosure and changes and modifications may be made therein within the scope of the following claims.

We claim:

1. A grinding apparatus comprising a base, work support means for rotatably supporting an annular workpiece, a grinding wheel assembly mounted for movement about a pivotal axis including an elongated pivot arm rotatably supporting a grinding wheel and pivotally mounted to the base at one terminal end, a stop member carried by the grinding wheel assembly closely adjacent the center of the grinding wheel, an infeed mechanism mounted on the base adapted to be engaged by the stop member of the grinding wheel assembly during the grinding cycle, hydraulic actuator means for pivoting the grinding wheel assembly about its pivotal axis in a feed direction to maintain firm contact of the stop member and infeed mechanism during the grinding cycle, said infeed mechanism including means controlling pivotal movement of the grinding wheel assembly toward the workpiece during the grinding cycle, the point of contact between said stop member and infeed mechanism being located close to the grinding wheel center to minimize deflection.

2. A grinding apparatus as claimed in claim 1 wherein the actuator means comprises a piston cylinder actuator wherein the cylinder is pivotally connected to the base and the piston is connected to the pivot arm.

3. A grinding apparatus comprising a base, work support means for rotatably supporting an annular workpiece, a grinding wheel assembly including an elongated pivot arm rotatably supporting a grinding wheel and pivotally mounted to the base at one terminal end, a stop member carried by the grinding wheel assembly and an infeed mechanism mounted on the base adapted to be engaged by the stop member of the grinding wheel assembly during the grinding cycle, said infeed mechanism comprising an internally threaded retract cylinder against which the stop member abuts during the grinding cycle, a feed screw threadedly engaging in the retract cylinder and means for actuating the feed screw to move the retract cylinder in a direction to permit advance of the grinding wheel during the grinding cycle.

4. A grinding apparatus comprising a base, work support means for rotatably supporting an annular workpiece for rotation about its axis, a grinding wheel assembly mounted for movement about a pivotal axis including an elongated pivot arm rotatably supporting a grinding wheel for rotation about its axis and pivotally mounted to its base at one terminal end, a stop member carried by the grinding wheel assembly closely adjacent the center of the grinding wheel, an infeed mechanism mounted on the base adapted to be engaged by the stop member of the grinding wheel assembly during the grinding cycle, hydraulic actuator means for pivoting the grinding wheel assembly about its pivotal axis in a feed direction to maintain firm contact of the stop member and infeed mechanism during the grinding cycle, said infeed mechanism including means controlling pivotal movement of the grinding wheel assembly toward the workpiece during the grinding cycle, the point of contact between said stop member and infeed mechanism being located close to the grinding wheel center to minimize deflection, the pivotal axis of the grinding wheel assembly is disposed in a first horizontal plane which is below a second horizontal plane through the axis of rotation of the workpiece and wherein the axis of rotation of the grinding wheel is in a third horizontal plane above said second horizontal plane of the workpiece during the grinding cycle whereby the grinding force is transferred to the base of said grinding apparatus.

5. A grinding apparatus comprising a base, work support means for rotatably supporting an annular workpiece, a grinding wheel assembly including a elongated pivot arm rotatably supporting a grinding wheel and pivotally mounted to the base at one terminal end, a stop member carried by the grinding wheel assembly, an infeed mechanism including a feed screw mounted on the base adapted to be engaged by the stop member of the grinding wheel assembly during the grinding cycle, said infeed mechanism including means controlling pivotal movement of the grinding wheel assembly toward the workpiece during the grinding cycle, a sizing device cooperatively associated with said grinding wheel assembly and control means operatively connecting the sizing device to said infeed mechanism to terminate rotation of said feed screw in a direction permitting advance of said grinding wheel assembly at the termination of the grinding cycle.

6. A grinding apparatus as claimed in claim 4 wherein said control means includes means for effecting movement of said grinding wheel assembly at a predetermined rate during a rough grinding portion of the grinding cycle and at a rate slower than said predetermined rate during a finish grind portion of the grinding cycle,

References Cited UNITED STATES PATENTS 2,028,315 1/1936 Bruhl et al. 51-105 2,467,161 4/1949 Sheeley 5198 2,478,562 8/1949 Binns et al 51103 2,647,347 8/1953 Blanchette 51-103 X 2,795,088 6/1957 SchonhOft et al 511 65 X 2,861,399 11/1958 Lundius 51165 X 3,280,512 10/1966 Seidel 51-103 X 3,290,830 12/1966 Ono 5l103 FOREIGN PATENTS 848,589 11/1939 France.

LESTER M. SWINGLE, Primary Examiner US. Cl. X.R. 

